A conventional technology of generating three-dimensional model of features (natural or artificial all the terrestrial objects) is known as the technology that takes three-dimensional point cloud data of the land surface obtained through an aerial laser scanner as the input data and classifies it into two parts, i.e. features and the ground based on their different frequency characteristics, and then calculates three-dimensional geographical coordinates of the contour polygon of each feature obtained from the classification, thereby generating three-dimensional model of all the features.
Patent Literature 1 discloses, as an example of the above stated technology, the method and system of generating three-dimensional urban spatial model by utilizing the data from laser scanner.
According to the technologies disclosed in Patent Literature 1, in general, the generated three-dimensional feature model is rough due to the limited resolution of laser data, and in this case there is a disadvantage that, in particular, the rooftop structure of a feature cannot be expressed highly precisely. For example, the rooftop part of a three-dimensional feature model generated based on laser data with the resolution of 1 m cannot express the details of the rooftop structure of an actual building.
In recent years, new technologies appear by generating digital surface model (DSM) at the same resolution as the input high-resolution stereo pair of aerial photographs, which enables the generation of finer three-dimensional data than laser data, and also finer expression of the rooftop structure of features. Moreover, the cost of aerial photogrammetry is lower than that of laser data.
Moreover, Patent Literature 2 discloses a technology of firstly taking images of buildings on the ground, while at the same time recording the longitude and latitude of the location where the images are taken, and then allowing an operator to specify the vertices of the structural planes of the building, finally calculating the three-dimensional coordinates of the specified vertices based on the images and the GPS information, thus generating a three-dimensional model of the building.
According to the technology of Patent Literature 2, a lot of manual works for each building is necessary, such as image shooting, vertices specification, etc., and thus the costs become large especially in the case of, for example, a broad residential street with high density of residential buildings. In addition, the image shooting on the ground has some limitations, such that a tall building in an urban district cannot be processed.
Under such circumstances, for example, Non-patent Literature 1 discloses a three-dimensional reconstruction technology to generate three-dimensional models of features by using the stereo pair of aerial photographs.
Non-patent Literature 1 discloses a technology of firstly detecting lines from the stereo pair of aerial photographs, secondly extracting line groups with special geometrical relationship like parallel or vertical relationship through a technology called perceptual grouping by analyzing the geometrical relationship between a line and its neighboring lines both in left and right images of the stereo pair, subsequently extracting features with rectangular contour, and thirdly obtaining the three-dimensional coordinates of the feature contour by stereo matching, thereby generating the three-dimensional model of all the features.
In addition, Non-patent Literature 2 discloses a technology similar to the technology in Non-patent Literature 1, that collects only edges associated with each feature through perceptual grouping to get the contour of each rectangular building, and obtains three-dimensional building model based on disparity map calculated in advance by stereo matching.